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Tailings are the fine-grained residue of the milling process in which the desired raw materials are extracted from the mined rock, and, due to mixing with water during this process, appear as slurries. The deposits of these residues in ponds or lagoons, usually confined by man-made dams, can present a serious threat, especially where there is improper handling and management. Technologies which use the sub-aqueous conventional upstream, centreline and downstream methods have left a legacy of many unstable tailings facilities with potentially liquefiable zones and steep slopes which are prone to erosion. The technology of producing high-density, very low-moisture thickened tailings, i.e. paste technology (PT), has made rapid progress from 1995 onwards, and offers significant economic incentives and environmental benefits. No particle segregation takes place during the thickening process; the paste material exhibits a much greater stability than conventional tailings; there is no pond on top of the deposit; the paste forms a gently sloping surface after placement which promotes the runoff of rain water; and the overall costs are lower than for conventional methods. Due to these features, PT, in many cases, offers a highly advantageous disposal technology, providing stable deposits and a reduced risk to humans and the environment. In certain cases, dry stacking, which has many similar advantageous features, is preferred. Concrete applications should be assessed on a case-by-case basis.

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